The Use of Score Tests for Frailty Variance Components in Recurrent Event DataSanjoy K. Sinha*
School of Mathematics and Statistics, Carleton University, Ottawa, ON, Canada
- *Corresponding Author:
- Sanjoy K. Sinha
School of Mathematics and Statistics
Ottawa, ON, K1S 5B6 Canada
E-mail: [email protected]
Received date: July 07, 2012; Accepted date: August 29, 2012; Published date: September 03, 2012
Citation: Sinha SK (2012) The Use of Score Tests for Frailty Variance Components in Recurrent Event Data. J Biomet Biostat S1:008.doi: 10.4172/2155-6180.S1-008
Copyright: © 2012 Sinha SK. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
In the analysis of recurrent event data, frailties are commonly used to model the dependence structure among repeated event times within an individual. Often it is of interest to test whether the variance component in a frailty model is zero. It is well-known that the usual asymptotic mixtures of chi-square distributions of the score statistics for testing constrained variance components do not necessarily hold. In this paper, we propose and explore a stochastic permutation score test based on randomly permuting the indices associated with the individuals of a survival model. An empirical study suggests that the proposed score test has approximately the correct level of significance and is more powerful than the asymptotic score test based on the mixture of chi-square distributions. The proposed test is illustrated using two sets of actual recurrence failure time data obtained from clinical experiments.